In many hydraulic applications it is necessary to monitor the pressure of the hydraulic system. Over-pressure conditions can be a constant hazard in certain hydraulic applications such as stamping and forging operations. In these operations, dies are driven in large presses to form and forge metal or plastic parts. Pressure transducers are used in the hydraulic system to monitor the loads on the equipment to insure proper and safe operation of the system. Over-pressure conditions of hydraulic systems can inadvertently be generated from very high transient pressure waves (or spikes) caused by the large pumps, cylinders and fast acting valves on these hydraulic machines. The spikes are usually of an unpredictable magnitude and duration, but pressures of two to ten times the expected pressure range are not uncommon.
Prior pressure transducers typically provided 150% of rated range protection against calibration damage (zero offset). Up to 500% protection was available before destruction of the pressure sensing device through rupture of the sensing diaphragm. Other prior systems increased the safe operating range of the pressure sensing transducer through various mechanical devices, such as set screws. Set screws limit the displacement of the diaphragm and increase the protection against calibration damage up to two to three times that of the rated range. The bursting pressure for the diaphragm is usually not increased by these mechanical devices. The use of set screws in particular, can actually decrease the bursting pressure limit due to the high stress area of the screw head.